LINQ查询错误- foreach循环中的where子句

Question

我写了一个LINQ查询，但是我在foreach循环中执行where子句时遇到了一些问题。

using (DataClasses1DataContext db = new DataClasses1DataContext(("ConnectionString")))
{
    Table<NOTIF_SCHED> NOTIF_SCHED_alias = db.GetTable<NOTIF_SCHED>();
    IQueryable<NOTIF_SCHED> notif_sched_data = from sched in NOTIF_SCHED_alias select sched;
    foreach (var notif_sched_data_value in notif_sched_data)
    {
        string a = notif_sched_data_value.NOTIF_RPT_ID.ToString();
        Table<mainframe_replication> mainframe_replications_alias = db.GetTable<mainframe_replication>();
        IQueryable<mainframe_replication> mainframe_replications_data =
            from mfrepl in mainframe_replications_alias
            where (mfrepl.RPT_ID.Equals(a))
            select mfrepl;
        foreach (var mainframe_replication_data_value in mainframe_replications_data)
        {
            Console.WriteLine("hi");
        }
    }
}

我不能在行中使用Where子句:

IQueryable<mainframe_replication> mainframe_replications_data =
    from mfrepl in mainframe_replications_alias
    where (mfrepl.RPT_ID.Equals(a))
    select mfrepl;**

请帮忙检查一下语法是否有问题

Answer 1

这应该做同样的事情，并且运行得更快:

using (DataClasses1DataContext db = new DataClasses1DataContext(("ConnectionString")))
{
    var ids = db.NOTIF_SCHEDs.Select(x=>x.NOTIF_RPT_ID).ToArray();
    var repl = db.mainframe_replication
        .Where(mfrepl=>ids.Contains(mfrepl.RPT_ID));
        foreach (var mainframe_replication_data_value in repl)
        {
            Console.WriteLine("hi");
        }
    }
}

如果NOTIF_RPT_ID不是字符串，而RPT_ID是字符串，你可以这样做:

using (DataClasses1DataContext db = new DataClasses1DataContext(("ConnectionString")))
{
    var ids = db.NOTIF_SCHEDs.Select(x=>x.NOTIF_RPT_ID.ToString()).ToArray();
    var repl = db.mainframe_replication
        .Where(mfrepl=>ids.Contains(mfrepl.RPT_ID));
        foreach (var mainframe_replication_data_value in repl)
        {
            Console.WriteLine("hi");
        }
    }
}